Fundamentals and applications of nanoparticle interactions and self-assembly

The subject of this thesis is the development and implementation of novel methods for measuring colloidal interactions, and the elucidation of how these interactions influence a variety of separation and assembly processes. Weak interactions between nanometer-sized particles can be measured by colloidal characterization techniques such as static light scattering. Two novel alternative methods, self-interaction chromatography and self-interaction nanoparticle spectroscopy, were developed to characterize weak protein interactions. Both techniques yielded measurements comparable to osmotic second virial coefficients obtained by light scattering for several proteins, but the self-interaction techniques are appreciably more efficient. These high-throughput screening tools were used to investigate the interaction behavior of several proteins that have proven difficult to crystallize previously. The extensive set of virial coefficients revealed a variety of surprising trends that provided important insights into previous difficulties in crystallizing these proteins. The corresponding phase behavior experiments confirmed previous findings that, in general, solution conditions conducive to crystallization correspond to weakly attractive interactions. Most importantly, a methodology for crystallizing proteins in a rational manner was demonstrated that should be applicable to proteins that have not been crystallized previously.; Self-interaction chromatography can also be adapted to measure protein cross-interactions directly. Virial cross coefficients measured for several model systems agreed with the small number of values in the literature.{09}The cross coefficient measurements were also found to correlate with diafiltration measurements for lysozyme in the presence of BSA using a membrane that was permeable only to lysozyme; when the cross-interactions were most attractive, the transmission of lysozyme was lowest, and vice versa.; Finally, the templated assembly of gold nanoparticles by latex microspheres was investigated as a method of synthesizing a new class of porous metallic materials. Colloidal crystals were assembled and backfilled with gold nanoparticles. The colloidal crystals could then be removed, producing a porous gold structure. The gold films possessed intriguing optical properties, and showed high sensitivity as surface-enhanced Raman spectroscopy substrates when used to detect several model compounds. This sensitivity was comparable to that of the best results achieved previously, although the films in this work were fabricated in a simpler and less expensive manner.